Renal Resistance on Hypothermic Machine Perfusion and Acceptance of Deceased Donor Kidney Allografts.

KEY POINTS: Terminal renal resistance added prognostic value to kidney donor profile index (KDPI), especially in KDPI >0.85 kidneys. Its effect was modest in KDPI ≤0.85 kidneys. Terminal renal resistance was found to be useful in guiding the acceptance of KDPI >0.85 kidneys on the basis of estimated post-transplant survival. Terminal renal resistance ≥0.3 triggered kidney nonuse regardless of KDPI, but KDPI ≤0.85 kidneys should not be declined on the basis of resistance alone.

BACKGROUND

Elevated terminal renal resistance on hypothermic machine perfusion is widely regarded as a marker of kidney quality and a trigger for kidney nonuse for transplantation, yet large-scale evidence is limited on whether terminal renal resistance adds prognostic value beyond kidney donor profile index (KDPI).

METHODS

Adult kidney-only transplants performed using hypothermic machine perfusion ( n =36,490) in the Organ Procurement and Transplantation Network database between March 31, 2015, and December 31, 2023, were included. Terminal renal resistance was categorized as <0.2, 0.2-0.3, 0.3-0.4, and ≥0.4 mm Hg/ml per minute. The primary outcome was 5-year graft survival. The association of terminal renal resistance with survival was analyzed to estimate the cutoff renal resistance for accepting high-KDPI (>0.85) kidneys. Utilization analyses were performed in a separate donor cohort of 15,524 kidneys recovered using hypothermic machine perfusion from eight organ procurement organizations.

RESULTS

Higher renal resistance was independently associated with worse 5-year graft survival (hazard ratio for graft loss=1.49 [≥0.4] versus <0.2; P < 0.001). The effect was modest in KDPI <0.35 kidneys and was strongest in KDPI >0.85 grafts. Renal resistance thresholds that were associated with better survival of using KDPI >0.85 kidneys differed on the basis of candidate estimated post-transplant survival (EPTS; renal resistance <0.2 for EPTS <0.35, <0.3 for EPTS 0.35-0.85, and <0.4 for EPTS >0.85). Utilization dropped sharply beyond a terminal renal resistance of 0.3 across all KDPI strata, disproportionate to the actual graft risk. Utilization of KDPI ≤0.85 grafts with renal resistance ≥0.30 could have yielded an estimated 357 (95% confidence interval, 304 to 377) additional transplants per year.

CONCLUSIONS

Terminal renal resistance was associated with long-term graft and patient survival, but this effect was clinically meaningful only in high-KDPI kidneys.